I have an aqua clear 110 hob filter on my 46gal tank. 57lbs of lr. the instructions for the filter say to change the carbon every month, the ceramic thingies every 2 months and the foam every 3 months but not to chnage all at once...my question is...do i really change the foam out? seems like that is where all the bacteria are---wouldn't that screw up my cycle?

The ceramic thingies are what's meant for the bio bacteria, though they cling onto anything porous and in good water flow. For a reef, a HOB filter is quite useless, IMO. So are canisters. The HOB you have could be good to run carbon for a week once a month, but other than that it really serves no purpose for the reef system. You don't want to run carbon 24/7 in a reef. Reef grade carbon for a week once a month is enough. I've learned that carbon can rob the system of needed trace elements.

All you need is a good protein skimmer and/or refugium.

To answser your question about the foam, it's best to rinse it in tank water to clean any nasty stuff on it and replace it when it starts to get raggy looking. You can set a new piece of foam in the water under good water flow for a couple of weeks before exchanging so the new foam cultivates some bacteria, but as mentioned above, HOB filters are worthless in a reef. The bulk of your bio are the rocks and substrate anyway. The need for a skimmer and/or refugium is to control proteins. An absolute must in a reef system.

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We, as a people, know so much more about outer space than we do about our own oceans. This lack of knowledge can very well spell the dangers that lay in wait for us.

The oceans surely would swallow us before a rock comes down to smite the planet of it's life.
Nov/2004